The invention relates to a device for displaying three-dimensional images in which N recorded images corresponding to N various spatial observation positions are displayed on one or more intermediate display screens and corresponding picture segments of the recorded images are displayed via a lens element of a viewing screen.
Such a device is disclosed in U.S. Pat. No. 4,214,257. In said specification, two recorded images are displayed on a color display screen of a cathode ray tube, the first recorded image being displayed by the odd field lines and the second recorded image being displayed by the even field lines. Each recorded image is built up from picture segments consisting of vertical image strips and the corresponding image strips of the recorded images are displayed in pairs via a viewing screen of vertical cylinder lenses. By associating each pair of corresponding image strips with a vertical cylinder lens of the viewing screen, it can be achieved that a viewer views the first recorded image with his left eye and views the second recorded image with his right eye. In this manner, a stereoscopic image is presented to the viewer by which three-dimensionality of the recorded scene is evoked perceptively.
However, in order to obtain a good stereoscopic image, it is necessary for an unambiguous relationship to exist between each pair of corresponding image strips and the lens element which is associated with said pair. This means that stringent requirements are imposed upon the accuracy with which the image strips are in registration with the vertical cylinder lenses.
In the known device, the picture selection is controlled electronically per field line and the place which the vertical image strips occupy on the intermediate display screen is determined by a shadow mask placed before the intermediate display screen. The electron beams, upon writing the odd field lines, display only the picture information of the first recorded image and, upon writing the even field lines, display only the picture information of the second recorded image on the intermediate display screen. In this manner, pairs of corresponding vertical image strips are displayed beside each other on the intermediate display screen. In this manner, however, it is particularly difficult to get the pairs of corresponding vertical image strips also in registration with the vertical cylinder lenses of the viewing screen.
Furthermore, in the known device, the viewing screen also forms an enveloping part of the cathode ray tube and should consequently have sufficient thickness of the required rigidity. The focal length of the cylinder lenses, however, then is approximately equal to the thickness of the viewing screen because the focal planes of the cylinder lenses coincide approximately with the intermediate display screen which in the known device is formed by a phosphor screen. However, a large focal length has for its result that when the viewer's head is displaced slightly in a direction transverse to the longitudinal direction of the cylinder lenses (i.e. the horizontal direction), picture reversal occurs from orthoscopic to pseudoscopic, which is experienced as annoying. In order to increase this so-called viewing angle, cylinder lenses of comparatively large transverse dimensions should be used, which, of course, is associated with loss of picture definition. These problems become even larger when three or more recorded images are used to produce a three-dimensional display which better corresponds to reality.